Introduction

Gastroenteritis (colloquially known by names names, including gastric flu, “gastro”, vomiting and diarrhoea, “food poisoning”) is a very common presentation to general practice and emergency departments, in people of all ages, but especially in children, or families with young children.

It is a broad term, but usually used to referred to an infective illness which causes diarrhoea, vomiting and often abdominal pain. The majority of cases are viral, and a smaller percentage are true “food poisoning” (usually bacterial, occasionally parasitic) related to improper preparation or storage of food.

It typically occurs in outbreaks in winter (often rotavirus or norovirus), and may cause hospital wards to be shut down during an outbreak.

In most patients with vomiting anddiarrhoea, gastroenteritis should be considered as the most likely diagnosis. In patients with vomiting only, or diarrhoea only, particularly in the presence of fever or abdominal pain, caution should be applied and a careful history and examination undertaken to look for other causes. In children in particular, vomiting alone can be a sign of a more serious underlying illness.

The cause is not usually identified – and most cases are self limiting and resolve in a few days. The treatment does not usually depend on the cause, and typically consists of managing nausea and vomiting and encouraging oral fluid intake. Severe cases of dehydration may require hospital admission for IV fluid administration.

In developing countries, gastroenteritis is a leading cause of death.

Epidemiology & Aetiology

Affects about 20% of the population each year

Viral infections cause 30-40% of cases in developed countries

In children, the proportion caused by viruses is much greater

Risk factors

Poor sanitation / poor personal hygiene

Immunocompromised patients

Poor food preparation

Undercooked

Reheated – reheating food correctly will kill bacteria, but will not destroy any toxins they left behind

Left at room temperature for too long

Particularly at risk foods include seafood

Causes

Viral causes are by far the most common. In the UK, norovirus – the “winter vomiting virus”is renowned for using outbreaks on hospital wards.

Common organisms include:

Viral causes

Norovirus

Rotavirus – very common in young children

Adenovirus – very common in young children

Enterovirus

Ebola – recent deadly outbreaks in Africa

Bacterial Causes

Campylobacter

Escherichia Coli

Salmonella

Shigella

Staphylococcus – usually the toxins from the bug rather than the bug itself

Specific investigations to rule out other causes – e.g USS or CT abdomen

Management

Indications for hospital admission

Signs of severe dehydration

Consider if not yet severely dehydration, but unable to retain any fluids orally

Consider if social circumstances may not be amenable to safe care at home – e.g. elderly or isolated, underlying medical conditions

Outpatient Management

Oral rehydration is the mainstay of treatment

In adults, there is no evidence that oral rehydration solutions (e.g. dioralyte, hydralyte) are any more effective than water, although they are frequently recommended

Titrate to urine output

In children, oral rehydration solutions should be used, or watered-down apples juice (5 parts water, one part apple juice) is an alternative. Children can pretty reluctant to drink the solutions. If parents are struggling, use a syringe, with small amounts regularly – e.g. 1ml/Kg every 5 minutes). Continue to offer breast milk if the child is usually feeding via this method

Aim for 50ml/Kg every 4 hours

Aim to record the fluid intake on a fluid chart

Vomiting is NOT a contraindication to oral rehydration – contrary to popular belief, it doesn’t “all come back up again” and significant amounts are often still absorbed

Consider IV fluids if not responding to oral intake

NG tube is an alternative in children

Food intake:

Guided by appetite

Small frequent meals

Avoid fatty and spicy foods

Plain starchy foods considered best

NO evidence for fasting or avoid solid food intake

In children – feed as directed by the child

Reducing the spread of infection

Frequent hadn’t washing is effective at reducing the spread of infection

Do not share towels

Wash any soiled bed sheets, separately from other clothes and at the highest temperature recommended on washing label

Norovirus is partially resistant to alcohol hand gel, and C. difficile spores are not killed by alcohol. As such, hand washing with soap and water is recommended

School / work exclusion

Exclude for 48 hours from the last episode of diarrhoea or vomiting

Some guidelines recommend 24 hours

Anti-emetics

Patient.co.uk states “not usually necessary in primary care” – my personal experience in primary care and as an Emergency Department Registrar in Australia is that they are VERY frequently prescribed – especially in children – in primary care and emergency departments.

Often ondansetron (private prescription only for this indication in both UK and Australia, and previously prohibitively expensive but now retails for <£5GBP or <$20AUD for 4 tablets of 4mg) is the most effective – 4mg single dose (or 2mg TDS in children between 8-16kgs, not recommended in children <8kgs, but in emergency departments sometimes given as 0.15mg/Kg doses). Particularly useful as it comes in an orally dispersible “wafer” which dissolves on or underneath the tongue and thus doesn’t require the patient to swallow a tablet with water in severe cases of vomiting. Often a single dose only is required – symptoms are usually much improved by 8 hours later when a second dose can be given if required.

Metoclopromide – 10mg TDS in adults is another option

Cyclizine – 50mg TDS – an antihistamine – frequently used for nausea and vomiting on the NHS – because it is cheap!

Anti-diarrhoea drugs – e.g. loperamide (“Immodium” or “gastro-stop”)

Not usually recommended

Are available over the counter and often patients have tried these before presentation

Carry a rare risk of bowel obstruction

Anecdotally in my practice seem to be associated with a longer duration of abdominal pain and bloating

Should NEVER be used if fevers, blood or mucus in stool

I rarely prescribe them if someone has an event they really can’t miss (e.g. wedding, funeral, job interview), with full disclosure of the above risks

Antibiotics are almost never indicated

Most cases are viral

Even in a bacterial cause, common bacterial causes – such as E Coli or shigella, then antibiotics can react with toxins and cause haemolytic uraemia syndrome and thus should still be avoided

Notifiable diseases

Be aware of the results of any stool MC+S samples – as many identifiable causes are notifiable diseases

Complications

Dehydration and electrolyte disturbance are the main complications

Haemolytic uraemia syndrome – rare. Features include acute kidney injury, haemolytic anaemia and thrombocytopenia. Usually occurs in very young children or frail elderly adults

Bacterial causes may cause reactive symptoms which are sometimes delayed in presentation by several weeks. These can include:

Arthritis

Carditis

Urticaria

Conjunctivitis

Salmonella is associated with a risk of systemic and secondary organ infection

Related Articles

Dr Tom Leach MBChB DCH EMCert(ACEM) currently works as a GP Registrar and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009.
Read full bio

1 Response

Really good web site. Helps me much starting as doc in Scotland, even with nearly 15 years as medicine man on the back. Good structure and well chosen topics. Sometimes links are some difficult, but guess thats normal.
Like it.